First off let me say that if there is already a post for this then I am sorry for re-posting it.

Step 1: Press up on the d-pad and go to the internet, go to travel and transport, then go to [ Register or Signin to view external links. ]

Step 2: Buy the Pegassi Bati 801 motorcycle

Step 3: Go to single player, then press start, go to online, and click solo session.

Step 4: Get on your Pegassi Bati 801 motorcycle and drive to the nearest Los Santos Customs.

Step 5. Buy as many upgrades for your bike as you can and sell it.

Step 6: Right when you sell it press start, then press LB and press (A) to go to the xbox gamer store, then press (B)

Step 7: This is the most important step! It will most likely say that Los Santos Customs is not excepting any vehicles right now so now all you do is have to wait for them to start excepting vehicles again. You can do missions or just go away for a while but if you do a mission make sure and you are doing it with other players make sure at the end you don't click on free mode but you click on (B) to exit. I had to wait 40 minutes for them to start selling again but when they start accepting again you can sell the vechicle over and over agin for as long as you want.

Step 8: When they start accepting again drive to the nearest Los Santos Customs with the bike and sell it. Right when you sell it press LB and go to the Xbox Games Store, when your at the Xbox Games Store just click (B) to exit. You should spawn very clost to that Los Santos Customs and you can just repeat the process.

I have made 20 million dollars off of this and I have only known about it for a day so if you are dedicated you can make A LOT OF MONEY.